Field
The present disclosure relates to power amplifiers in radio-frequency (RF) applications.
Description of the Related Art
Power amplifiers (PAs) are widely used in various communication networks to set the transmission power level of an information-bearing signal transmitted by one device to another device. For example, power amplifiers are used to set the pulse energy emitted by pulsed lasers in optical communication networks. Power amplifiers are also used in the radio frequency (RF) front-end components of wireless carrier network devices—such as base stations, repeaters, and mobile client devices (e.g. mobile phones, smartphones, tablet computers, etc.)—to set the power level of a wireless signal transmitted through an antenna. PAs are also used in local area networks of homes and offices to support both wired and wireless connectivity of servers, computers, laptops, and peripheral devices such as photocopiers and printers.
In some implementations, PAs use a boost converter for DC-to-DC power conversion when the PAs output voltage should be greater than its input voltage. Typically, a boost converter with a compensated error-amplifier has an intrinsic soft-start feature. With the capacitor at the error-amplifier output slowly being charged up, the duty cycle of the boost is slowly increased, leading to a slow increase of the boost output voltage. In some implementations, in order to use a boost converter to power a high-voltage PA, the boost converter is specified to ramp up at a rate of 570 mV/μs in order to avoid any signal distortion at the output of the PA. The fast ramp-rate of the boost output voltage not only limits the value of the output capacitor, but also posts a challenge on circuit design and architecture to work against the slow soft-start nature of the error amplifier.